问c++运算符重载，调用析构函数

EN

class num{
public:
    virtual void setValue(int)=0;
    static int db;
    num(){}
    ~num(){}
};

int num::db = 0;

class int32: public num{
public:
    // GET
    int getValue();

    // SET
    void setValue(int f);

    // constructor
    int32()
    {
        cout << "Construction..."<<endl;
        this->value = 0;num::db++;
    }

    // destructor
    ~int32()
    {
        cout << "destruction..."<<endl;
        num::db--;
    }

    // operators
    int32 operator++(int);
    int32 operator++(void);

protected:
    int value;
};

int32 int32::operator ++()
{
    this->value++;
    return *this;
}

int32 int32::operator ++(int)
{
    this->value++;
    return *this;
}

int main()
{
    int32 i;
    i.setValue(20);

    cout << (i++).getValue()<<endl;
    cout << (++i).getValue()<<endl;

    cout << num::db;

    cout << endl << "End of execution.";
    return 1;
}